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Ultimaker 2+ lines not touching in walls

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Hi all,

I've had this issue for a while, with what i thought was underextrusion but I've tried almost everything to remedy.

Slowing down and increasing temperature / extrusion multiplier of course makes them touch, but this isn't really a solution.

I have replaced TFM to new.

I have tightened the short belts.

I have checked and ensured Bowden are not too far into head.

I have measured hot end spacing to 16.8mm

I have reeled the spool from below to reduce tension.

The extruder is in good condition with no wear on hobbed bolt.

The only thing I can think of is that maybe my long belts aren't tight enough? They're not slack but I'm not sure how tight they should be.

Below is a video hoping to show the belt tension with a light touch. Is that too loose, should I replace? They are less tight than the short belts.

 

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It's not a tension issue. If the belts are loose you get a different issue that's hard to explain. Well one factor is that a cube is not square and circles are not round. There is a tensioner in each block hidden inside. If you loosen the set screw on each pulley the spring should take up the tension. Anyway I don't think this is your issue.

What do you mean about the bowden? It's tricky to get the bowden all the way into the head. It should be touching the white teflon part. Normally when I take my bowden out it takes several tries to get it all the way down into the white teflon part.

The video is great but I'd like to see a photo of what you are not happy about.

I'm sure you have underextrusion. It's just a very common problem. First give yourself a test case that can be printed continuously so that changing something gives you results in seconds. That way you can test 100 times as many things than if you are printing an entire print between each test change.

Try printing at 10mm/sec when you get to the problem area. Raise temperature to 240C and set flow at 140%. If that doesn't fix it then maybe you are right and it's not underextrusion. Once you believe that it really is underextrusion here is a list of potential causes.

CAUSES FOR UNDEREXTRUSION AND HOW TO TEST FOR THEM AND REMEDY THEM

As far as underextrusion causes - there's just so damn many. none of the issues seem to cause more than 20% of problems so you need to know the top 5 issues to cover 75% of the possibilities and 1/4 people still won't have the right issue. Some of the top issues:

1) Print slower and hotter! Here are top recommended speeds for .2mm layers (twice as fast for .1mm layers) and .4mm nozzle:

20mm/sec at 200C

30mm/sec at 210C

40mm/sec at 225C

50mm/sec at 240C

The printer can do double these speeds but with huge difficulty and usually with a loss in part quality due to underextrusion. Different colors print best at quite different temperatures and due to imperfect temp sensors, some printers print 10C cool so use these values as an initial starting guideline and if you are still underextruding try raising the temp. But don't go over 240C with PLA.

2) Shell width confusion. Shell width must be a multiple of nozzle size. For example if nozzle size is .4mm and shell width is 1mm cura will make the printer do 2 passes with .5mm line width which is possible but requires you to slow down much more to make a .5mm line out of a .4mm nozzle. If you really want this then set nozzle size to .5mm so it's clear what you are asking Cura to do for you.

3) Isolator - this is most common if you've printed extra hot (>240C) for a few hours or regular temps (220C) for 500 hours. It gets soft and compresses the filament under pressure. It's the white part touching the heater block. It's very hard to test when not under full pressure (spring and bowden) so sometimes it's best to just replace it. Also if you notice parts of it are very soft (the blacker end where it touches higher heat) then it's too old and needs replacing.

4) Curved filament at end of spool - if you are past half way on spool, try a fresh spool as a test.

5) curved angle feeding into feeder - put the filament on the floor -makes a MASSIVE difference.

6) Head too tight? Bizarrely MANY people loosen the 4 screws on the head by just a bit maybe 1/2 mm and suddenly they can print just fine! Has to do with pressure on the white teflon isolator.

6b) Bowden pushing too hard - for the same reason you don't want the bowden pushing too hard on the isolator.

6c) Spring pushing too hard. Although you want a gap you want as small as possible a gap between teflon isolator and steel isolator nut such that the spring is compressed as little as possible.

7) clogged nozzle - the number one problem of course - even if it seems clear. There can be build up on the inside of the nozzle that only burning with a flame can turn to ash and remove. Sometimes a grain of sand gets in there but that's more obvious (it just won't print). Atomic method (cold pull) helps but occasionally you need to remove the entire heater block/nozzle assembly and use flame. Or soak it in acetone overnight (after removing 90% of the material with cold pull).

8) Temp Sensor bad - even the good ones vary by +/- 5C and bad ones can be any amount off - they usually read high and a working sensor can (rarely) fail high slowly over time. Meaning the sensor thinks you are at 220C but actually you are at 170C. At 170C the plastic is so viscous it can barely get out of the nozzle. You can verify your temp sensor using this simple video at youtube - on you tube search for this: mrZbX-SfftU

9) feeder spring issues - too tight, too loose

10) Other feeder issues, one of the nuts holding machine together often interferes with the feeder motor tilting it enough so that it still works but not very well. Other things that tilt the feeder motor, sleeve misaligned so it doesn't get a good grip. Gunk clogging the mechanism in there.

11) Filament diameter too big - 3mm is too much. 3mm filament is usually 2.85mm nominal or sometimes 2.9mm +/- .05. But some manufacturers (especially in china) make true 3.0mm filament with a tolerance of .1mm which is useless in an Ultimaker. It will print for a few meters and then clog so tight in the bowden you will have to remove the bowden from both ends to get the filament out. Throw that filament in the trash! It will save you weeks of pain

11b) Something wedged in with the filament. I was setting up 5 printers at once and ran filament change on all of them. One was slowly moving the filament through the tube and was almost to the head when I pushed the button and it sped up and ground the filament badly. I didn't think it was a problem and went ahead and printed something but there was a ground up spot followed by a flap of filament that got jammed in the bowden tube. Having the "plus" upgrade or using the IRobertI feeder helps you feel this with your hand by sliding the filament through the bowden a bit to see if it is stuck.

12) Hot weather. If air is above 30C or even possibly 25C, the air temperature combined with the extruder temperature can soften the filament inside the feeder such that it is getting squeezed flat as it passes through the feeder - this is obvious as you can see the problem in the bowden. The fix is to add a desk fan blowing on the back of the printer. Not an issue on the UM2 "plus" series.

13) Crimped bowden. At least one person had an issue where the bowden was crimped a bit too much at the feeder and although the printer worked fine when new it eventually got worse and had underextrusion on random layers. it's easy to pull the bowden out of the feeder end and examine it.

14) Small nozzle. Rumor has it some of the .4mm nozzles are closer to .35mm. Not sure if this is actually true. I'm a bit skeptical but try a .6mm nozzle maybe.

15) CF filament. The knurled sleeve in the extruder can get ground down smooth - particularly from carbon fill. 4 spools of CF will destroy not just nozzles but the knurled sleeve also. Look at it visually where the filament touches the "pyramids". Make sure the pyramids are sharp.

16) Hot feeder driver. I've seen a more recent problem in the forums (>=2015) where people's stepper drivers get too hot - this is mostly a problem with the Z axis but also with the feeder. The high temps means the driver appears to shut down for a well under a second - maybe there is a temp sensor built into the driver chip? The solution from Ultimaker is that they lowered all the currents to their stepper drivers in the newer firmware. Another solution is to remove the cover and use desk fan to get a tiny bit of air movement under there. TinkerMarlin lets you set the currents from the menu system or you can send a gcode to lower the current. Ultimaker lowered the default currents in July of 2015 from 1300ma to 1200ma for X,Y,Z but left extruder at 1250. Other people (I think the support team of a major reseller but I forget) recommend X,Y,Z go down to 1000mA.

M907 E1250

Above sets the extruder max current to the default - 1250mA. So try 900mA. This will only change until next power cycle so if you like your new value and want to save it use M500. You can just put these into an otherwise empty gcode file and "print" this and it will change. Or get tinkergnome marlin! You will wonder how you lived without it: https://github.com/TinkerGnome/Ultimaker2Marlin/releases

M907 E900

M500

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OK Will go through that (although I had been using this as somewhat of a guide for fixes to date).

I typically can get extrusion at acceptable, walls touching levels by in creasing temps / extrusion multiplier and so I'll now use your approach to dialing in the correct speed for temp etc. I had no idea speed / temp had such vast differences - I may just be guilty of over time increasing both speed and layer height without much thought to extrusion - assuming the UM will just push through more and more.

So do you think belts look sloppy or is that the correct tension - I hear it's fairly cheap to replace them and after already doing the TFM I wonder if I should go ahead, or are they still pretty good (not sure on original tension as bought second hand).

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I hear replacing the belts on a UM2 is a nightmare job that will very likely (70%?) destroy at least one of your 4 blocks. Even if you don't hurt them too much they will never hold together as well as when they are new.

Instead, if one side of the belt is tighter than the other I would loosen both screws on a long belt and let the belt auto tension itself then re-tighten the set screws. And tighten the hell out of those things.

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It's hard to tell how tight they are in your video because I don't know how hard you are pushing and "not hard" is not accurate enough, lol. It would have been better to play them like a string. Then I could compare musical pitch to mine.

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